A number of councils use Parkmobile, and Wandsworth Council provides a geographical number: 020 3003 2523
http://www.wandsworth.gov.uk/Home/EnvironmentandTransport/Parking/paybyphonepark...As I'm withholding my number, it doesn't get any further than telling me off for doing so, which is the same response when calling 0870 7305005, 0871 2212369 & 0871 2883203. The same recording is on 020 3003 2524. Numbers 020 3003 2525 /6 etc go through to the helpdesk even with a withheld number, so they are not identical to 2523 and 2524.
It may be that the number for Wandsworth is suitable for all areas and I have listed it as such in the database.
Please provide feedback on whether these numbers work for all areas operating Parkmobile.